Manually-actuated reduced pressure treatment system with audible leak indicator

ABSTRACT

Illustrative embodiments of new and useful systems and methods for reduced-pressure therapy are described. One example embodiment is a manually-actuated pump for applying reduced-pressure therapy. The pump generally comprises a charging chamber, a regulated chamber, and a regulator passage between the charging chamber and the regulated chamber. A valve body controls fluid communication through the regulator passage, and a regulator spring may be engaged with the valve body to bias the valve body against a differential between a pressure in the regulated chamber and an ambient pressure. The regulator passage may have a bore size adapted deflect the valve body to cause an audible indication of a leak.

The present invention is a continuation of U.S. patent application Ser.No. 14/156,256, filed Jan. 15, 2014, which claims the benefit, under 35USC § 119(e), of the filing of U.S. Provisional Patent Application No.61/753,356, entitled “MANUALLY-ACTUATED REDUCED PRESSURE TREATMENTSYSTEM WITH AUDIBLE LEAK INDICATOR,” filed Jan. 16, 2013, by Locke etal., which is incorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The subject matter described herein relates generally to reducedpressure treatment systems. More particularly, but without limitation,the subject matter relates to a manually-actuated reduced pressuretreatment system having capabilities for providing a regulated pressureto a tissue site and an audible indication of a leak.

2. Description of Related Art

Clinical studies and practice have shown that reducing pressure inproximity to a tissue site can augment and accelerate growth of newtissue at the tissue site. The applications of this phenomenon arenumerous, but it has proven particularly advantageous for treatingwounds. Regardless of the etiology of a wound, whether trauma, surgery,or another cause, proper care of the wound is important to the outcome.Treatment of wounds with reduced pressure is commonly referred to as“reduced-pressure therapy,” but may also be known by other names,including “negative pressure wound therapy,” “vacuum-assisted closure,”or “vacuum therapy,” for example. Reduced-pressure therapy may provide anumber of benefits, including migration of epithelial and subcutaneoustissues, improved blood flow, and micro-deformation of tissue at a woundsite. Together, these benefits can increase development of granulationtissue and reduce healing times.

While the clinical benefits of reduced-pressure therapy are widelyknown, the cost and complexity of reduced-pressure therapy can be alimiting factor in its application, and the development and operation ofreduced-pressure systems, components, and processes continues to presentsignificant challenges to manufacturers, healthcare providers, andpatients.

SUMMARY

Illustrative embodiments of new and useful systems and methods forreduced-pressure therapy are described herein. One example embodiment isa manually-actuated pump for applying reduced-pressure therapy, whichgenerally comprises a charging chamber, a regulated chamber, and aregulator passage between the charging chamber and the regulatedchamber. A valve body is adapted to control fluid communication throughthe regulator passage, and a regulator spring may be engaged with thevalve body to bias the valve body against a differential between apressure in the regulated chamber and an ambient pressure. The regulatorpassage may have a bore size adapted to deflect the valve body, leavinga gap between the valve body and the regulator passage to cause anaudible indication of a leak above a threshold. The gap in some exampleembodiments may be less than 0.1 mm, and the bore size preferably has adiameter in a range of about 1 mm to about 1.5 mm. A conduit may also becoupled to the outlet port, and the conduit preferably has a lumen witha diameter of about 1.2 mm.

Other illustrative embodiments of an apparatus are described having apiston chamber having a closed end, a piston disposed within the pistonchamber and being movable between an extended position and a compressedposition, a charging chamber disposed between the piston and the closedend, and a regulated chamber. A biasing member may be adapted to biasthe piston toward the extended position, and a valve member can beadapted to allow fluid to exit the charging chamber as the piston movestoward the compressed position and to prevent fluid from entering thecharging chamber as the piston moves toward the extended position. Aregulator member may be provided to regulate fluid communication througha passage between the charging chamber and the regulated chamber,wherein the passage has a bore size adapted to deflect the regulatormember cause an audible indication of a leak greater than apredetermined threshold.

Illustrative embodiments of methods for providing reduced pressuretreatment are also described, including methods that store a chargingpressure within a charging chamber, deliver a desired therapy pressurefrom a regulated chamber to a tissue site, reduce the pressure withinthe regulated chamber by allowing fluid communication between thecharging chamber and the regulated chamber when a pressure within theregulated chamber exceeds the desired therapy pressure, and provide anaudible indication of a leak.

Other objects, features, and advantages of the illustrative embodimentswill become apparent with reference to the drawings and detaileddescription that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective view of a reduced pressure treatmentsystem according to an illustrative embodiment, the reduced pressuretreatment system having a reduced pressure pump adapted to deliver areduced pressure to a dressing positioned at a tissue site;

FIG. 2 depicts a cross-sectional front view of the dressing of FIG. 1taken at 2-2;

FIG. 3 illustrates a schematic of a reduced pressure treatment apparatusaccording to an illustrative embodiment, the reduced pressure treatmentapparatus having a charging chamber, a regulated chamber, and aregulator member, the regulator member being shown in an open position;

FIG. 4 depicts a schematic of the reduced pressure treatment apparatusof FIG. 3, the regulator member being shown in a closed position;

FIG. 5 illustrates a schematic of a piston-driven device for use withthe reduced pressure treatment apparatus of FIG. 3 to charge thecharging chamber with a reduced pressure, the piston-driven devicehaving a piston shown in a compressed position;

FIG. 6 depicts a schematic of the piston-driven device of FIG. 5 withthe piston shown in an extended position;

FIG. 7 illustrates a side perspective view of a reduced pressuretreatment apparatus according to an illustrative embodiment;

FIG. 8 depicts a front view of the reduced pressure treatment apparatusof FIG. 7;

FIG. 9 illustrates an exploded side perspective view of the reducedpressure treatment apparatus of FIG. 7;

FIG. 10 depicts an exploded rear perspective view of the reducedpressure treatment apparatus of FIG. 7;

FIG. 11 illustrates a cross-sectional side view of the reduced pressuretreatment apparatus of FIG. 8 taken at 11-11, the reduced pressuretreatment apparatus shown in an extended position;

FIG. 12 depicts a top-rear perspective view of a piston of the reducedpressure treatment apparatus of FIG. 7;

FIG. 13 illustrates a bottom-rear perspective view of the piston of FIG.12;

FIG. 14 depicts a top-rear perspective view of a seal of the reducedpressure treatment apparatus of FIG. 7;

FIG. 15 illustrates a bottom-rear perspective view of the seal of FIG.14;

FIG. 16 depicts a top-rear perspective view of a second barrel of thereduced pressure treatment apparatus of FIG. 7;

FIG. 17 illustrates a bottom-rear perspective view of the second barrelof FIG. 16;

FIG. 18 depicts a cross-sectional side view of the reduced pressuretreatment apparatus of FIG. 7, the reduced pressure treatment apparatusshown in a compressed position;

FIG. 19 illustrates an enlarged cross-sectional view of the reducedpressure treatment apparatus of FIG. 18, the reduced pressure treatmentapparatus having a valve body shown in a closed position;

FIG. 20 depicts an enlarged cross-sectional view of the reduced pressuretreatment apparatus of FIG. 19 with the valve body shown in an openposition;

FIG. 20A depicts an enlarged cross-sectional view, similar to that ofFIG. 20, of a reduced pressure treatment apparatus according to anillustrative embodiment;

FIG. 21 illustrates a perspective view of a reduced pressure treatmentapparatus according to an illustrative embodiment;

FIG. 22 depicts a cross-sectional side view of the reduced pressuretreatment apparatus of FIG. 21 taken at 22-22; and

FIG. 23 illustrates a graph of regulated chamber pressure vs. time for areduced pressure treatment apparatus.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

New and useful systems, methods, and apparatuses associated withproviding reduced-pressure therapy are set forth in the appended claims.Objectives, advantages, and a preferred mode of making and using thesystems, methods, and apparatuses may be understood best by reference tothe following detailed description in conjunction with the accompanyingdrawings. The description provides information that enables a personskilled in the art to make and use the claimed subject matter, but mayomit certain details already well-known in the art. Moreover,descriptions of various alternatives using terms such as “or” do notnecessarily require mutual exclusivity unless clearly required by thecontext. The claimed subject matter may also encompass alternativeembodiments, variations, and equivalents not specifically described indetail. The following detailed description should therefore be taken asillustrative and not limiting.

The example embodiments may also be described herein in the context ofreduced-pressure therapy applications, but many of the features andadvantages are readily applicable to other environments and industries.Spatial relationships between various elements or to the spatialorientation of various elements may be described as depicted in theattached drawings. In general, such relationships or orientations assumea frame of reference consistent with or relative to a patient in aposition to receive reduced-pressure therapy. However, as should berecognized by those skilled in the art, this frame of reference ismerely a descriptive expedient rather than a strict prescription.

The term “reduced pressure” as used herein generally refers to apressure less than the ambient pressure at a tissue site that is beingsubjected to treatment. In most cases, this reduced pressure will beless than the atmospheric pressure at which the patient is located.Alternatively, the reduced pressure may be less than a hydrostaticpressure associated with tissue at the tissue site. Although the terms“vacuum” and “negative pressure” may be used to describe the pressureapplied to the tissue site, the actual pressure reduction applied to thetissue site may be significantly less than the pressure reductionnormally associated with a complete vacuum. Reduced pressure mayinitially generate fluid flow in the area of the tissue site. As thehydrostatic pressure around the tissue site approaches the desiredreduced pressure, the flow may subside, and the reduced pressure is thenmaintained. Unless otherwise indicated, values of pressure stated hereinare gauge pressures. Similarly, references to increases in reducedpressure typically refer to a decrease in absolute pressure, whiledecreases in reduced pressure typically refer to an increase in absolutepressure.

The term “tissue site” as used herein refers to a wound or defectlocated on or within any tissue, including but not limited to, bonetissue, adipose tissue, muscle tissue, neural tissue, dermal tissue,vascular tissue, connective tissue, cartilage, tendons, or ligaments.The term “tissue site” may further refer to areas of any tissue that arenot necessarily wounded or defective, but are instead areas in which itis desired to add or promote the growth of additional tissue. Forexample, reduced pressure tissue treatment may be used in certain tissueareas to grow additional tissue that may be harvested and transplantedto another tissue location.

In general, reduced-pressure therapy can be beneficial for wounds of allseverity, but the cost and complexity of reduced-pressure therapysystems often limit the application of reduced-pressure therapy tolarge, highly-exudating wounds present on patients undergoing acute orchronic care, as well as other severe wounds that are not readilysusceptible to healing without application of reduced pressure. Forexample, the complexity of conventional reduced-pressure therapy systemscan limit the ability of a person with little or no specializedknowledge from administering reduced-pressure therapy. The size of manyreduced-pressure therapy systems may also impair mobility. Manyreduced-pressure therapy systems also require careful cleaning aftereach treatment, and may require electrical components or other powereddevices to supply the reduced pressure for treatment.

Eliminating power requirements can increase mobility, and generallyreduce cost, as well. For example, a manually-actuated ormanually-charged pump can be used as a source of reduced pressureinstead of an electrically-powered pump. However, leaks in a dressingcan gradually erode energy stored in pump. Large leaks are also commonwhen a dressing is first applied. A manually-actuated reduced-pressuretherapy system can be particularly sensitive to leaks because thecapacity of such a system to generate reduced pressure is typically morelimited than electrically-powered pumps. The presence of a leak at adressing can quickly dissipate the therapeutic pressure generated by apump.

As described herein, a reduced-pressure treatment system 100 canovercome these shortcomings and others by providing audible feedback offlow indicative of a leak. Referring to FIGS. 1 and 2, a reducedpressure treatment system 100 according to an illustrative embodimentincludes a reduced pressure dressing 104 positioned at a tissue site 108of a patient. The reduced pressure dressing 104 is fluidly connected toa reduced pressure source 110 by a conduit 112. The conduit 112 mayfluidly communicate with the reduced pressure dressing 104 through atubing adapter 116. In the embodiment illustrated in FIG. 1, the reducedpressure source 110 is a manually-actuated pump such as the regulatedpressure pumps described herein. In another implementation, the reducedpressure source 110 may include pressure regulation capabilities but mayinitially be charged or re-charged to a selected reduced pressure by areduced pressure or vacuum pump that is driven by an electric motor. Instill another embodiment, the reduced pressure source 110 may be chargedto the selected reduced pressure by a wall suction port such as areavailable in hospitals and other medical facilities.

The reduced pressure source 110 may be housed within or used inconjunction with a reduced pressure treatment unit (not shown), whichmay also contain sensors, processing units, alarm indicators, memory,databases, software, display units, and user interfaces that furtherfacilitate the application of reduced pressure treatment to the tissuesite 108. In one example, a sensor or switch (not shown) may be disposedat or near the reduced pressure source 110 to determine a sourcepressure generated by the reduced pressure source 110. The sensor maycommunicate with a processing unit that monitors and controls thereduced pressure that is delivered by the reduced pressure source 110.Delivery of reduced pressure to the reduced pressure dressing 104 andtissue site 108 encourages new tissue growth by maintaining drainage ofexudate from the tissue site, increasing blood flow to tissuessurrounding the tissue site, and creating microstrain at the tissuesite.

The reduced pressure dressing 104 includes a distribution manifold 120adapted to be positioned at the tissue site 108, and a seal layer 122 toseal the reduced pressure dressing 104 around the tissue site 108. Acover 124, or drape, is positioned over the distribution manifold 120and the seal layer to maintain reduced pressure beneath the cover 124 atthe tissue site. The cover 124 may extend beyond a perimeter of thetissue site and may include an adhesive or bonding agent on the cover124 to secure the cover to tissue adjacent the tissue site. In oneembodiment, the adhesive disposed on cover 124 may be used in lieu ofthe seal layer 122, however, the seal layer 122 may be used inconjunction with the adhesive of the cover 124 to improve sealing of thecover 124 at the tissue site 108. In another embodiment, the seal layer122 may be used in lieu of adhesive disposed on cover 124.

The distribution manifold 120 of the reduced pressure dressing 104 isadapted to contact the tissue site 108. The distribution manifold 120may be partially or fully in contact with the tissue site 108 beingtreated by the reduced pressure dressing 104. When the tissue site 108is a wound, the distribution manifold 120 may partially or fully fillthe wound.

The distribution manifold 120 may be any size, shape, or thicknessdepending on a variety of factors, such as the type of treatment beingimplemented or the nature and size of the tissue site 108. For example,the size and shape of the distribution manifold 120 may be customized bya user to cover a particular portion of the tissue site 108, or to fillor partially fill the tissue site 108. Although the distributionmanifold 120 illustrated in FIG. 3 has a square shape, the distributionmanifold 120 may be shaped as a circle, oval, polygon, an irregularshape, or any other shape.

In one illustrative embodiment, the distribution manifold 120 is a foammaterial that distributes reduced pressure to the tissue site 108 whenthe distribution manifold 120 is in contact with or near the tissue site108. The foam material may be either hydrophobic or hydrophilic. In onenon-limiting example, the distribution manifold 120 is an open-cell,reticulated polyurethane foam such as GranuFoam® dressing available fromKinetic Concepts, Inc. of San Antonio, Tex.

In the example in which the distribution manifold 120 is made from ahydrophilic material, the distribution manifold 120 also functions towick fluid away from the tissue site 108, while continuing to providereduced pressure to the tissue site 108 as a manifold. The wickingproperties of the distribution manifold 120 draw fluid away from thetissue site 108 by capillary flow or other wicking mechanisms. Anexample of a hydrophilic foam is a polyvinyl alcohol, open-cell foamsuch as V.A.C. WhiteFoam® dressing available from Kinetic Concepts, Inc.of San Antonio, Tex. Other hydrophilic foams may include those made frompolyether. Other foams that may exhibit hydrophilic characteristicsinclude hydrophobic foams that have been treated or coated to providehydrophilicity.

The distribution manifold 120 may further promote granulation at thetissue site 108 when a reduced pressure is applied through the reducedpressure dressing 104. For example, any or all of the surfaces of thedistribution manifold 120 may have an uneven, coarse, or jagged profilethat causes microstrains and stresses at the tissue site 108 whenreduced pressure is applied through the distribution manifold 120. Thesemicrostrains and stresses have been shown to increase new tissue growth.

In one embodiment, the distribution manifold 120 may be constructed frombioresorbable materials that do not have to be removed from a patient'sbody following use of the reduced pressure dressing 104. Suitablebioresorbable materials may include, without limitation, a polymericblend of polylactic acid (PLA) and polyglycolic acid (PGA). Thepolymeric blend may also include without limitation polycarbonates,polyfumarates, and capralactones. The distribution manifold 120 mayfurther serve as a scaffold for new cell-growth, or a scaffold materialmay be used in conjunction with the distribution manifold 120 to promotecell-growth. A scaffold is a substance or structure used to enhance orpromote the growth of cells or formation of tissue, such as athree-dimensional porous structure that provides a template for cellgrowth. Illustrative examples of scaffold materials include calciumphosphate, collagen, PLA/PGA, coral hydroxy apatites, carbonates, orprocessed allograft materials.

Referring to FIGS. 3 and 4, a reduced pressure treatment apparatus 150,or reduced pressure pump, or reduced pressure source, is schematicallyillustrated and includes a charging chamber 154 fluidly connected by apassage 156, or conduit, to a regulated chamber 158. A regulator member162 is operably associated with the passage 156 to selectively allow orprevent fluid communication between the charging chamber 154 and theregulated chamber 158. In the embodiment illustrated in FIGS. 3 and 4,the regulator member 162 includes a piston 164 that is disposed withinthe regulated chamber 158. The regulator member 162 further includes aregulator spring 166 to bias the piston 164 toward an open position asillustrated in FIG. 3. In the open position, the piston 164 allows fluidcommunication through the passage 156. In a closed position (shown inFIG. 4), the piston 164 prevents or at least substantially reduces fluidcommunication through the passage 156.

As previously noted, the charging chamber 154 is fluidly connected tothe regulated chamber 158 by passage 156. The charging chamber 154 mayinclude an inlet 170 for introduction of a reduced pressure to thecharging chamber 154, or as explained below, the charging chamber 154may by operably associated with a piston-driven or other device tocharge the charging chamber 154 with the reduced pressure. The chargingchamber 154 is well suited to receive the reduced pressure from a devicethat is manually-actuated, or alternatively that is powered byelectrical or other means.

The regulated chamber 158 is fluidly connected by a conduit 172 to adressing 174. In one embodiment, the conduit 172 and dressing 174 may besimilar to conduit 112 and dressing 104. When reduced pressure treatmentis applied to the dressing 174 and a tissue site, it is desired todeliver a reduced pressure to dressing 174 that is about equal to adesired therapy pressure. To accomplish this, the charging chamber 154stores a first pressure that is less than an ambient pressure. Theregulated chamber 158 stores a second pressure that is also less thanthe ambient pressure. The first pressure stored in the charging chamber154 is less than the second pressure stored in the regulated chamber158.

When the second pressure is less than or equal to the desired therapypressure, a counteracting force on the piston is able to overcome abiasing force exerted by the regulator spring 166 on the piston 164. Thecounteracting force on the piston is a result of a pressure differentialacross opposite sides of the piston 164. On a first side 176 of thepiston 164, the ambient pressure (e.g. atmospheric pressure) surroundingthe reduced pressure treatment apparatus 150 acts on the piston 164. Ona second side 178 of the piston 164, the second pressure within theregulated chamber 158 acts on the piston. Since the second pressure isless than the ambient pressure, the counteracting force acts on thefirst side 176 of the piston 164 against the biasing force of theregulator spring 166. When the second pressure in the regulated chamber158 is less than or equal to the desired therapy pressure, the piston164 moves to and remains in the closed position.

If the second pressure in the regulated chamber 158 rises above (i.e.exceeds) the desired therapy pressure, possibly due to fluid leaks atthe dressing 174 or within the reduced pressure treatment apparatus 150,the piston 164 is biased back to the open position by the regulatorspring 166. In the open position, fluid communication is allowed betweenthe charging chamber 154 and the regulated chamber 158. Since the firstpressure in the charging chamber 154 is less than the second pressure inthe regulated chamber 158, the second pressure in the regulated chamber158 drops until the desired therapy pressure is reached, at which pointthe piston 164 again moves to the closed position. In one embodiment,the first pressure stored in the charging chamber 154 is about −150 mmHg, and the desired therapy pressure is about −125 mm Hg.

If a dressing has a small leak, regulator member 162 can maintain thetherapy pressure. However, regulator member 162 may not be able tomaintain the therapy pressure if a leak exceeds a certain tolerance,which is dependent upon the size of the restrictions on the entry andexit sides of the regulated chamber 158. For example, passage 156 andconduit 172 may be sized such that a leak exceeding a threshold causesregulator member 162 to remain partially open with a gap betweenregulator member 162 and passage 156 that allows a steady flow of airthrough passage 156 and conduit 172. Moreover, the sizes of passage 156and conduit 172 may be calibrated such that the flow of air through thegap causes an audible note, alerting an operator of an unexpected lossof therapeutic pressure.

Referring to FIGS. 5 and 6, a piston-driven device 180 is provided forcharging a charging chamber 182 similar to charging chamber 154. Thepiston-driven device 180 includes a piston 184 disposed within thecharging chamber 182. This piston 184 is capable of reciprocal movementbetween a compressed position (see FIG. 5) and an extended position(see. FIG. 6). A piston spring 188 or other biasing member is operablyassociated within the piston 184 to bias the piston 184 toward theextended position.

To charge the charging chamber 182, the piston 184 is moved to thecompressed position. A seal 190 or other valve member allows fluidwithin the charging chamber 182 to exit the charging chamber 182 as avolume of the charging chamber 182 decreases. After moving the piston184 to the compressed position, the piston spring 188 attempts to returnthe piston 184 to the extended position. As the volume of the chargingchamber 182 increases, the seal 190 prevents fluid from entering thecharging chamber 182 past the seal 190, which results in a pressure dropwithin the charging chamber 182. After the piston 184 has movedcompletely to the extended position, the piston 184 may be moved againto the compressed position to recharge the charging chamber 182 with areduced pressure.

The piston-driven device 180 may be manually-actuated by a usercompressing the piston 184. Alternatively, the piston 184 may beactuated by an electrical, hydraulic, or pneumatic actuator. For all ofthe charging chambers described herein, it should be noted that reducedpressure may be supplied to the charging chamber by manual orelectrically powered means.

Referring to FIGS. 7 and 8, a reduced pressure treatment apparatus, orreduced pressure source 211 according to an illustrative embodiment is amanually-actuated pump having a first, or outer barrel 215 and a second,or inner barrel 219. The first barrel 215 includes a passage 223 (seeFIG. 9) having a closed end and an open end. The passage 223 may bedefined by a substantially cylindrical wall. The passage 223 slidinglyreceives the second barrel 219 through the open end of the first barrel215, and the second barrel 219 is movable between an extended positionand a compressed position. While the first and second barrels areillustrated as having substantially cylindrical shapes, the shapes ofthe barrels could be any other shape that permits operation of thedevice.

In the extended position, the reduced pressure source 211 is dischargedand does not actively deliver or supply a reduced pressure. In thecompressed position, the reduced pressure source 211 is primed orcharged, and the reduced pressure source 211 is capable of delivering areduced pressure. An outlet port 227 is provided on the second barrel219 and is adapted for fluid communication with a delivery tube or otherconduit, which may be similar to delivery tube 135, such that reducedpressure generated by the reduced pressure source 211 may be deliveredto the tissue site.

Referring to FIGS. 9-11, the reduced pressure source 211 furtherincludes a barrel ring 229, a piston 231, and a seal 235. The barrelring 229 is positioned at the open end of the first barrel 215 tocircumscribe the second barrel 219. The barrel ring 229 eliminates largegaps between the first barrel 215 and the second barrel 219 at the openend of the first barrel 215. When the reduced pressure source 211 isassembled, the piston 231 and seal 235 are slidingly received within thepassage 223 of the first barrel 215. Both the piston 231 and the seal235 are positioned in the passage 223 between the second barrel 219 andthe closed end of the first barrel 215, the seal 235 being positionedbetween the second barrel 219 and the piston 231.

Referring more specifically to FIG. 11, the first barrel 215 includes aprotrusion 239 extending from the closed end of the first barrel 215into the passage 223. A piston spring 243 or other biasing member ispositioned within the passage 223 and is received at one end of thepiston spring 243 by the protrusion 239. The protrusion 239 reduceslateral movement of the piston spring 243 within the passage 223. Anopposite end of the piston spring 243 is received against the piston231. The piston spring 243 biases the piston 231, the seal 235, and thesecond barrel 219 toward the extended position.

Referring again to FIGS. 9-11, but also to FIGS. 12 and 13, the piston231 includes an outer wall 247 and an inner wall 251 joined by an outerfloor 253. An annulus 255 is defined between the outer wall 247 and theinner wall 251, and a plurality of radial supports 259 are positionedbetween the outer wall 247 and the inner wall 251 in the annulus 255.The radial supports 259 provide additional rigidity to the piston 231,yet the presence of the annulus 255 as well as the sizes and spacing ofthe radial supports 259 within the annulus 255 reduces the weight of thepiston 231 as compared to a single-wall piston that includes no annulus.However, it should be apparent that either piston design would besuitable for the reduced pressure source described herein.

A plurality of guides 263 is disposed on the piston 231, and in oneembodiment, one of the guides 263 is disposed on each radial support259. As described in more detail herein, the guides 263 serve to alignthe piston 231 relative to the seal 235 and the second barrel 219. Theguides 263 further serve to secure the piston 231 to the second barrel219 by means of a friction fit.

The piston 231 further includes an inner bowl 267 that is defined by theinner wall 251 and an inner floor 271. In one embodiment, the innerfloor 271 may be two-tiered or multi-tiered as illustrated in FIG. 11,but the inner floor 271 may instead be single-tiered and/orsubstantially planar. The inner floor 271 may be positioned such that arecess 273 is defined beneath the inner floor 271 to receive an end ofthe piston spring 243 (see FIGS. 11 and 13). A regulator passage 275passes through the inner floor 271. A valve seat 279 may be positionedin the inner bowl 267 near the regulator passage 275 such that fluidcommunication through the regulator passage 275 may be selectivelycontrolled by selective engagement of the valve seat 279 with a valvebody (described in more detail with reference to FIG. 15).

A well 283 is positioned in the annulus 255 of the piston 231, and achannel 287 is fluidly connected between the well 283 and the inner bowl267. The channel 287 allows fluid communication between the well 283 andthe inner bowl 267.

Referring still to FIGS. 9-11, but also to FIGS. 14 and 15, the seal 235includes a central portion 291 that is circumscribed by a skirt portion295. A plurality of guidance apertures 299 are disposed in the centralportion 291 to receive the guides 263 of the piston 231 when the reducedpressure source 211 is assembled. A communication aperture 301 issimilarly disposed in the central portion 291, and in one embodiment,the communication aperture 301 is radially spaced an equal distance froma center of the seal as the guidance apertures 299. The communicationaperture 301 permits fluid communication through the central portion 291of the seal 235 and with the well 283 of the piston 231 upon assembly.

The skirt portion 295 of the seal 235 extends axially and radiallyoutward from the central portion 291. As illustrated in FIG. 11, theradially-outward-extending skirt portion 295 engages an inner surface305 of the first barrel 215 to permit unidirectional fluid communicationpast the seal 235. In other words, the skirt portion 295 of the seal 235allows fluid to flow past the skirt portion 295 when the fluid flow isdirected from the side of the seal 235 on which the piston 231 isdisposed toward the opposite side of the seal 235. The skirt portion295, however, substantially prevents fluid flow in the oppositedirection. While the skirt portion of the seal effectively controlsfluid communication past the skirt portion 295, a valve member such as,for example, a check valve or other valve could instead be used toperform this function.

As illustrated in more detail in FIGS. 11 and 15, a valve body 303 ispositioned on the central portion 291 of the seal 235. Although valvebodies of many types, shapes and sizes may be used, the valve body 303may be cone-shaped with an apex 309 that is adapted to sealingly engagethe valve seat 279 of the piston 231. While the valve body 303 isillustrated as being an integral part of the seal 235, the valve body303 may alternatively be a separate component from the seal 235 that isprovided to engage the valve seat 279.

In one embodiment, both the seal 235 and the valve body 303 are madefrom an elastomeric material, which could include without limitation amedical grade silicone. While many different materials may be used toconstruct, form, or otherwise create the seal 235 and valve body 303, itis preferred that a flexible material be used to improve the sealingproperties of the skirt portion 295 with the inner surface 305 and thevalve body 303 with the valve seat 279.

Referring more specifically to FIG. 11, a regulator spring 307 isprovided to bias the valve body 303 away from the piston 231 and thevalve seat 279. One end of the regulator spring 307 may be positionedconcentrically around the valve seat 279 within the inner bowl 267 ofthe piston 231, while another end of the regulator spring 307 may bepositioned around the valve body 303. The biasing force provided by theregulator spring 307 urges the valve body 303 toward an open position inwhich fluid communication is permitted through the regulator passage275. In one embodiment, when the spring 307 biases the valve body 303toward the open position, only the central portion 291 of the seal 235moves upward due to the flexibility of the seal (see FIG. 20). Inanother embodiment, the biasing force of the spring 307 may move theentire seal 235 toward the open position as illustrated in FIG. 20A.

Referring again to FIGS. 9-11, but also to FIGS. 16 and 17, the secondbarrel 219 includes a first housing portion 311 and a second housingportion 315. The first housing portion 311 includes an outer shell 319having an aperture 323 disposed near an open end of the first housingportion 311. A floor 327 is integrally formed with or otherwiseconnected to the outer shell 319 on an end of the first housing portion311 opposite the open end. A passage 331 may be centrally disposed inthe floor 327. A boss 333 is integrated with or connected to the firsthousing portion 311. The boss 333 includes the outlet port 227, which isphysically aligned with the aperture 323 to allow a delivery tube to befluidly connected to the outlet port 227. In one embodiment, the boss323 is a ninety degree fluid fitting that permits the outlet port 227 tofluidly communicate with a conduit 335 positioned within the firsthousing portion 311. The conduit 335 may be a rigid conduit that isformed from the same or similar material to that of the outer shell, orin one alternative embodiment, the conduit 335 may be flexible.

Referring more specifically to FIG. 17, a plurality of guidanceapertures 337 are disposed in the floor 327 of the first housing portion311. When the reduced pressure source 211 is assembled, the guidanceapertures 337 receive the guides 263 of the piston 231 to ensure thatthe second barrel 219 remains aligned with the piston 231. A frictionfit between the guides 263 and guidance apertures 337 assist in securingthe relative positions of the piston 231 and the second barrel 219. Itshould be readily apparent, however, that the piston 231 and the secondbarrel 219 may be secured by alternative means. A communication aperture338 is also disposed in the floor 327 to allow fluid communication withthe conduit 335 through the floor 327.

The second housing portion 315 may include an end cap 339 integrally orotherwise connected to a guide 343. Together, the end cap 339 and guide343 slidingly engage the outer shell 319 of the first housing portion311 to create a substantially closed second barrel 219 (with theexception of various apertures and passages). While the second barrel219 may be constructed from fewer components, the existence of the firsthousing portion 311 and the second housing portion 315 allows easieraccess within the second barrel 219 and also allows easier assembly ofthe reduced pressure source 211. Additional advantages regarding thesliding engagement of the first housing portion 311 and the secondhousing portion 315 are explained in more detail below.

A shaft 347 extends from the end cap 339 and includes an engagement end349 opposite the end cap 339. When the second barrel 219 is assembled,the shaft may be substantially coaxial to a longitudinal axis of thesecond barrel 219 and extend through the passage 331 in the floor 327 ofthe first housing portion 311. A spring 351 is positioned within thesecond barrel 219 such that one end of the spring 351 bears upon thefloor 327 of the first housing portion 311 and another end of the spring351 bears upon the shaft 347 or another portion of the second housingportion 315. The spring 351 biases the shaft 347 and other portions ofthe second housing portion 315 toward a disengaged position (seeposition of shaft 347 in FIG. 11) in which the engagement end 349 of theshaft 347 does not bear upon the seal 235 or valve body 303. The slidingrelationship and engagement between the first and second housingportions 311, 315 allows a user to exert a force on the second housingportion (against the biasing force of the spring 351) to move the secondhousing portion 315 to an engaged position. In the engaged position, theengagement end 345 of the shaft 347 bears upon the seal 235 above thevalve body 303 (see FIG. 18), which forces the valve body 303 againstthe valve seat 279, thereby preventing fluid communication through theregulator passage 275.

When the reduced pressure source 211 is assembled, as illustrated inFIG. 11, a charging chamber 355 is defined within the first barrel 215beneath the piston 231. A regulated chamber 359 is defined within theinner bowl 267 of the piston 231 beneath the seal 235. The regulatorpassage 275 allows selective fluid communication between the chargingchamber 355 and the regulated chamber 359 depending on the position ofthe valve body 303. The regulated chamber 359 fluidly communicates withthe well 283 of the piston 231 through the channel 287. The well 283 isaligned with the communication aperture 301 of the seal 235 and thecommunication aperture 338 of the first housing portion 311, whichallows fluid communication between the well 283 and the conduit 335 andoutlet port 227 of the second barrel 219.

While the regulator passage 275 is illustrated as being disposed withinthe piston 231, the regulator passage 275 could instead be routedthrough the wall of the first barrel 215. The regulator passage 275could be any conduit that is suitable for allowing fluid communicationbetween the chambers.

In operation, the reduced pressure source 211 is capable of being usedwith other components of a reduced pressure treatment system similar tothose of reduced pressure treatment system 100 (see FIG. 1). The outletport 227 of the reduced pressure source 211 is adapted to be connectedto a delivery tube or other conduit that is fluidly connected to atissue site. Although a fluid canister could be integrated into thereduced pressure source 211, in one embodiment, the reduced pressuresource 211 is not intended to collect wound exudates or other fluidswithin any internal chamber. In one embodiment, the reduced pressuresource 211 may either be used with low-exudating wounds, or analternative collection system such as an external canister or absorptivedressing may be used to collect fluids.

Referring to FIGS. 11 and 18, the extended position (see FIG. 11) andthe compressed position (see FIG. 18) of the reduced pressure source 211are illustrated. In the extended position, the reduced pressure source211 is not “charged” and is thus not capable of delivering reducedpressure to the outlet port 227. To prime the reduced pressure source211, the second barrel 219 is manually compressed into the first barrel215 by a user such that the reduced pressure source 211 is placed in thecompressed position. The force exerted by the user on the second barrel219 must be greater than the biasing force provided by the piston spring243. As the second barrel 219 compresses within the first barrel 215 andmoves toward the closed end of the first barrel 215, the force beingexerted on the second barrel 219 by the user is also transmitted to theseal 235 and piston 231. The movement of the second barrel 219, the seal235, and the piston 231 into the compressed position decreases thevolume of the charging chamber 355. As the volume of the chargingchamber 355 decreases, the pressure in the charging chamber 355increases, but air and other gases within the charging chamber 355 areallowed to escape past the skirt portion 295 of the seal 235 due to theincreased pressure within the charging chamber 355.

When the user releases the compressive force exerted upon the secondbarrel 219, the biasing force exerted by the piston spring 243 on thepiston 231 moves the piston 231, the seal 235, and the second barrel 219toward the extended position. As this movement occurs, the volume of thecharging chamber 355 increases. Since the skirt portion 295 of the seal235 allows only unidirectional flow, air and other gases are notpermitted to enter the charging chamber 355 past the skirt portion 295.A resulting drop in pressure (i.e., a generation of reduced pressure)occurs within the charging chamber 355 as the volume increases. Theamount of reduced pressure generated within the charging chamber 355 isdependent on the spring constant of the piston spring 243 and theintegrity of the seal 235. In one embodiment, it is desired to generatea reduced pressure that is greater (i.e., a lower absolute pressure)than the amount of reduced pressure to be supplied to the tissue site.For example, if it is desired to provide 125 mmHg of reduced pressure tothe tissue site, it may be desirable to have the charging chamber 355charged to 150 mmHg of reduced pressure.

The regulated chamber 359 is used to generate the desired therapypressure that is delivered to the outlet port 227 and the tissue site.When the reduced pressure within the charging chamber 355 is greaterthan the reduced pressure within the regulated chamber 359 and when thereduced pressure in the regulated chamber 359 is less than the desiredtherapy pressure, the upward force on the seal 235 (exerted by theincreased absolute pressure in the regulated chamber 359 and the biasingforce of the regulator spring 307, both against the atmosphere pressureexerted downward on the seal 235) moves the valve body 303 into the openposition (see FIG. 20), thereby allowing fluid communication between thecharging chamber 355 and the regulated chamber 359. The charging chamber355 continues to charge the regulated chamber 359 with reduced pressure(i.e., the absolute pressure in the regulated chamber 359 continues todrop) until the reduced pressure in the regulated chamber 359, balancedagainst the atmospheric pressure above the seal 235, is sufficient tocounteract the biasing force of the regulator spring 307 and move thevalve body into the closed position (see FIG. 19). When the regulatedchamber 359 is charged with the desired therapy pressure, this pressuremay be delivered to the outlet port as detailed previously.

When the reduced pressure source 211 is initially connected to adelivery tube and tissue site for treatment, it will likely be necessaryto compress the second barrel 219 within the first barrel 215 multipletimes. As each compression stroke is completed, the reduced pressuregenerated within the charging chamber 355 will pull air and any othergases from the delivery tube and the tissue site until the pressurewithin the tube and at the tissue site begins to approach the desiredtherapy pressure.

As the reduced pressure source 211 is being primed by one or morecompressions, it is important that air and other positively-pressurizedgases being pushed out of the charging chamber 355 are pushed past theskirt portion 295 of the seal 235 and not into the regulated chamber359. Positively pressurized gas flow to the regulated chamber 359 maytransfer to the delivery tube and the tissue site, which wouldcounteract the reduced pressure that is then being applied to the tissuesite. To prevent positively pressurized gas from entering the regulatedchamber 359, the shaft 347 is provided to engage the seal 235 and valvebody 303. As the second barrel 219 is compressed within the first barrel215, the second housing portion 315 moves relative to the first housingportion 311 so that the shaft 347 exerts a force on the valve body 303that holds the valve body 303 in the closed position. Since the shaft347 remains engaged during the entire compression, or charging stroke ofthe reduced pressure source 211, the air within the charging chamber 355is vented past the seal 235 and not into the regulated chamber 359.

While the reduced pressure source 211, including the first barrel 215,the second barrel 219, the piston 231, and the seal 235, have beendescribed herein as being cylindrical, it will be readily apparent thatall of these components may be any size or shape. Additionally, therelative positions of the valve seat 279 and the valve body 303 may bevaried in some embodiments.

If a dressing, delivery tube, or other component has a small leak, valvebody 303 can maintain a therapeutic pressure. For example, regulatedchamber 359 may be adapted to compensate for leaks that are less thanabout 1 L/min. However, valve body 303 may not be able to maintain thetherapy pressure if a leak exceeds such a limit, which is generallydependent upon the size of the restrictions on the entry and exit sidesof the regulated chamber 359.

The flow leaving regulated chamber 359 can be controlled by adjustingthe bore size of regulator passage 275, and the flow coming in can becontrolled by adjusting the size of the bore of a number of componentsin the fluid path, such as the conduit 112, tubing adapter 116, oroutlet port 227. The size of the bores can be balanced such that aflow-induced drop in reduced-pressure in regulated chamber 359 deflectsvalve body 303, leaving a gap between valve body 303 and regulatorpassage 275. Thus, if a leak is increasing and exceeds a predeterminedor configurable leak threshold, the decrease in reduced pressure inregulated chamber 359 may partially open valve body 303. If a leak isdecreasing but exceeds the leak threshold, the drop in reduced pressuremay partially close valve body 303, but still leave a gap. In someillustrative embodiments, the gap between valve body 303 and regulatorpassage 275 is less than 0.1 mm. Optionally, the bore sizes can bebalanced so that valve body 303 remains open if no dressing isconnected. Moreover, the bore sizes may be calibrated such that a flowof air through the gap produces an audible indicator, alerting anoperator of an unexpected loss of therapeutic pressure. For example, aleak threshold may represent a leak rate that is sufficient to interferewith a prescribed therapy, and many applications may have a leakthreshold of about 0.8 L/min. An audible indicator may be produced atthis threshold if the diameter of regulator passage 275 is in the rangeof about 1 mm to about 1.5 mm and conduit 112 has a lumen size of about1.2 mm over a length of about 500 mm to 800 mm. The size of the gap(e.g., the distance between apex 309 and regulator passage 275) may becalibrated so that the pitch of the audible note changes as flowdecreases or increases, thereby differentiating the size or rate of aleak.

In other illustrative embodiments, the flow through the system can becontrolled with additional components, such as filters, which mayinclude membranes, sintered porous materials, fibers, woven, ornon-woven materials, for example. Valve body 303 and regulator passage275 may also be designed to accentuate the audible feedback.

Referring to FIGS. 21 and 22, a reduced pressure treatment system 511includes a reduced pressure treatment apparatus 513 for delivering areduced pressure to a dressing 515 positioned at a tissue site 517. Thereduced pressure treatment apparatus includes a first flexible bladder521 and a second flexible bladder 523. The flexible bladders 521, 523are preferably made from an elastomeric material such as, for example, asilicone polymer, rubber, or another elastomeric material. The firstflexible bladder 521 includes a compressible chamber 527 in which isdisposed a biasing member 529. The second flexible bladder 523 includesa charging chamber 535 in which is disposed a biasing member 537. Thebiasing members 529, 537 may be any device that provides a biasing forceto resist collapse of the chambers 527, 535. In one embodiment, thebiasing members 529, 537 may be a porous foam that allows flow of fluidwithin or through the chambers 527, 535, but resists collapse when thechambers are exposed to a pressure less than an ambient pressuresurrounding the reduced pressure treatment apparatus 513.

The first flexible bladder 521 includes a one-way valve 541 to allowexpulsion of air from the compressible chamber 527 when the firstflexible bladder is 521 is compressed by a user. As the biasing member529 in the compressible chamber 527 attempts to move the first flexiblebladder 521 back to an extended position, the one-way valve 541 preventsor substantially reduces fluid from entering the compressible chamber527 through the one-way valve 541. Instead, fluid enters thecompressible chamber 527 through a one-way valve 551 positioned betweenthe first flexible bladder 521 and the second flexible bladder 523. Thisfluid is pulled from the charging chamber 535 into the compressiblechamber 527 to create a reduced pressure within the charging chamber535. The first flexible bladder 521 may be compressed and allowed toexpand several times to create the desired amount of reduced pressure inthe charging chamber 535. In one embodiment, the biasing member 537 inthe charging chamber 535 is a porous foam that is more resistant tocollapse than the biasing member 529 disposed in the compressiblechamber 527. This configuration allows the charging chamber 535 toresist collapse such that a greater reduced pressure may be stored inthe charging chamber 535.

The charging chamber 535 is positioned in fluid communication with thedressing 515 to deliver a reduced pressure to the tissue site 517. Aregulator member 561 is positioned between the charging chamber 535 andthe tissue site 517 to regulate pressure delivered by the chargingchamber 535 to the tissue site 517. The regulator member 561 may besimilar to other regulators described herein, or may be any other typeof regulator or device capable of regulating pressure. In oneembodiment, it is desired that a pressure within the charging chamber535 be less than the ambient pressure and less than a desired therapypressure that is to be delivered to the tissue site 517. The regulatormember 561 ensures that pressure delivered to the tissue site 517 doesnot drop below the desired therapy pressure. If the pressure supplied tothe tissue 517 begins to exceed the desired therapy pressure (i.e. morereduced pressure is needed), the regulator opens to allow fluidcommunication between the charging chamber 535 and the tissue site 517.

In the embodiment illustrated in FIGS. 21 and 22, the reduced pressuretreatment apparatus has been described as having a charging chambersimilar in some respects to other embodiments described herein. While awell-defined regulated chamber has not been described in this particularembodiment, a regulated chamber exists either within the dressing 515 atwhich regulated pressure is maintained, or within a fluid conduitfluidly connecting the regulator member 561 to the dressing 515.

Referring to FIG. 23, a graph is provided that illustrates the changesin pressure over time within a regulated chamber such as the regulatedchambers described herein. The ability of a charging chamber to rechargethe regulated chamber allows the pressure within the regulated chamberto vary little from the desired therapy pressure during operation of thereduced pressure source.

It should be apparent from the foregoing that an invention havingsignificant advantages has been provided. While the invention is shownin only a few of its forms, it is not just limited but is susceptible tovarious changes and modifications without departing from the spiritthereof.

What is claimed is:
 1. A reduced-pressure treatment apparatus fordelivering a reduced pressure to a dressing positioned at a tissue site,the reduced-pressure treatment apparatus comprising: a first flexiblebladder having a compressible chamber; a first biasing member disposedin the compressible chamber; a first one-way valve fluidly coupled tothe first flexible bladder; a second flexible bladder having a chargingchamber configured to be fluidly coupled to the dressing; a secondbiasing member disposed in the charging chamber; a second one-way valvefluidly coupled to the first flexible bladder and the second flexiblebladder; wherein compression of the first flexible bladder draws fluidfrom the charging chamber, developing a reduced pressure in the chargingchamber.
 2. The reduced-pressure treatment apparatus of claim 1, wherethe first flexible bladder and the second flexible bladder are formedfrom an elastomeric material.
 3. The reduced-pressure treatmentapparatus of claim 1, wherein the first flexible bladder and the secondflexible bladder are formed form at least one of a silicone polymer andrubber.
 4. The reduced-pressure treatment apparatus of claim 1, whereinthe first biasing member and the second biasing member comprise a porousfoam.
 5. The reduced-pressure treatment apparatus of claim 4, whereinthe porous foam is configured to distribute fluid through the porousfoam and resist collapse if exposed to a pressure less than an ambientpressure surrounding the reduced-pressure treatment apparatus.
 6. Thereduced-pressure treatment apparatus of claim 1, wherein the firstone-way valve is configured to permit flow of fluid out of thecompressible chamber and to prevent fluid flow into the compressiblechamber through the first one-way valve.
 7. The reduced-pressuretreatment apparatus of claim 1, wherein the second one-way valve isconfigured to permit fluid flow from the charging chamber to thecompressible chamber and to prevent fluid flow from the compressiblechamber to the charging chamber.
 8. The reduced-pressure treatmentapparatus of claim 1, wherein the second biasing member is stiffer thanthe first biasing member.
 9. The reduced-pressure treatment apparatus ofclaim 1, further comprising a regulator fluidly coupled between thecharging chamber and the dressing.
 10. The reduced-pressure treatmentapparatus of claim 9, wherein the regulator comprises: a regulatorpassage between the charging chamber and the dressing; a valve bodyadapted to control fluid communication through the regulator passage;and a regulator spring engaged with the valve body to bias the valvebody against a differential between a pressure in the dressing and anambient pressure.
 11. The reduced-pressure treatment apparatus of claim10, wherein the regulator passage has a bore size adapted to deflect thevalve body to cause an audible indication of a leak that exceeds apredetermined threshold.
 12. A reduced-pressure treatment system fordelivering a reduced pressure to a tissue site, the reduced-pressuretreatment system comprising: a dressing configured to be positionedadjacent the tissue site; a reduced-pressure treatment apparatusconfigured to be fluidly coupled to the dressing, the reduced-pressuretreatment apparatus comprising: a first flexible bladder having acompressible chamber; a first biasing member disposed in thecompressible chamber; a first one-way valve fluidly coupled to the firstflexible bladder; a second flexible bladder having a charging chamberconfigured to be fluidly coupled to the dressing; a second biasingmember disposed in the charging chamber; a second one-way valve fluidlycoupled to the first flexible bladder and the second flexible bladder;wherein compression of the first flexible bladder draws fluid from thecharging chamber, developing a reduced pressure in the charging chamber.13. The reduced-pressure treatment system of claim 12, wherein the firstbiasing member and the second biasing member comprise a porous foamconfigured to distribute fluid through the porous foam and resistcollapse if exposed to a pressure less than an ambient pressuresurrounding the reduced-pressure treatment apparatus.
 14. Thereduced-pressure treatment system of claim 12, wherein the first one-wayvalve is configured to permit flow of fluid out of the compressiblechamber and to prevent fluid flow into the compressible chamber throughthe first one-way valve.
 15. The reduced-pressure treatment system ofclaim 12, wherein the second one-way valve is configured to permit fluidflow from the charging chamber to the compressible chamber and toprevent fluid flow from the compressible chamber to the chargingchamber.
 16. The reduced-pressure treatment system of claim 12, whereinthe second biasing member is stiffer than the first biasing member. 17.The reduced-pressure treatment system of claim 12, further comprising aregulator fluidly coupled between the charging chamber and the dressing,the regulator comprising: a regulator passage between the chargingchamber and the dressing; a valve body adapted to control fluidcommunication through the regulator passage; and a regulator springengaged with the valve body to bias the valve body against adifferential between a pressure in the dressing and an ambient pressure.18. The reduced-pressure treatment system of claim 17, wherein theregulator passage has a bore size adapted to deflect the valve body tocause an audible indication of a leak that exceeds a predeterminedthreshold.
 19. A method for treating a tissue site with reducedpressure, the method comprising: providing a reduced-pressure treatmentapparatus comprising: a first flexible bladder having a compressiblechamber; a first biasing member disposed in the compressible chamber; afirst one-way valve fluidly coupled to the first flexible bladder; asecond flexible bladder having a charging chamber; a second biasingmember disposed in the charging chamber; a second one-way valve fluidlycoupled to the first flexible bladder and the second flexible bladder;fluidly coupling the charging chamber of the reduced-pressure treatmentapparatus to a dressing disposed adjacent to a tissue site; compressingthe first flexible bladder to draw fluid from the charging chamber ofthe second flexible bladder, thereby generating a reduced-pressure inthe charging chamber; and communicating the reduced-pressure in thecharging chamber to the dressing.
 20. The method of claim 19, furthercomprising: providing a regulator; fluidly coupling the regulatorbetween the charging chamber and the dressing; and regulating thereduced pressure communicated to the dressing to maintain the dressingat a therapy pressure.